In a radio communication system that employs OFDM (Orthogonal Frequency Division Multiplexing) such as LTE (Long Term Evolution) standardized by 3GPP (Third Generation Partnership Project), MIMO (Multiple Input Multiple Output) may be employed. In carrying out the MIMO employing SFBC (Space Frequency Block Coding) or spatial multiplexing, in consideration of MIMO demodulation at a receiving side, a sending side transmits a radio signal in a manner such that a frequency and time of known reference signals transmitted in each layer do not overlap each other.